Conventionally, position detecting devices have been known as devices that detect a rotational angle of a throttle valve of an electronic control throttle device for a vehicle, a rotational angle of an EGR valve of an exhaust gas recirculation valve device, or a rotational angle of an accelerator pedal of an accelerator device. For example, Patent Literature 1 (JP 2007-155617 A) discloses a position detecting device including a magnet, an IC substrate, two vertical Hall elements, and a lateral Hall element. The magnet generates a magnetic field having magnet flux lines in a direction perpendicular to a rotational axis of detection object. The IC substrate has a plate shape and is disposed in the magnetic field. The two vertical Hall elements are disposed in one surface of the IC substrate to detect a magnetic flux in a direction parallel to the one surface. The lateral Hall element detects a magnetic flux in a direction perpendicular to the one surface.
However, in the position detecting device described in Patent Literature 1, the three Hall elements can detect a magnetic field (hereinafter, referred to as “external magnetic field”) generated by members other than the magnet. Due to the external magnetic field, accuracy of detecting a rotational angle may be decreased. Furthermore, since the IC substrate is arranged so that the one surface of the IC substrate extends along the magnetic flux lines of the magnetic field formed by the magnet, the size is increased in a direction perpendicular to the rotational axis. As a result, the size of the position detecting device may be increased.
In view of the above, it is an objective of the present disclosure to provide a position detecting device where deterioration of accuracy of detecting a rotational angle due to the external magnetic field can be suppressed while decreasing the size thereof.